Chemical dating of minerals

elective courses

(in Polish) Podstawowa wiedza z zakresu petrologii i mineralogii; bierna znajomość j. angielskiego na poziomie przynajmniej B2.

The tutorial presents the methods of chemical dating of minerals and thus indirectly the methods of dating both crystalline and sedimentary rocks containing these minerals. Applied are methods available in the laboratories at the Faculty of Geology, including electron microprobe with cathodoluminescence and electron scanning microscopy. All stages leading to a reliable age determination are presented in details, step by step, both in crystalline and detritic sedimentary rocks (where applicable). The final result of the research are age determinations of the investigated mineral phases. Critical assessment of the obtained results are an important part of the work.

Chemical dating of minerals is a field that enables to obtain information on the age of thermal events in the history of the investigated phase due to the application of advanced analytical techniques and, what is important, without employing expensive isotopic methods. Detailed chemical microanalysis with the use of electron probe (EPMA) is sufficient to obtain the crystallisation age of the investigated mineral (or part of it). The aim of the tutorial is to lead the student through all stages of the dating process and its interpretation

1. Geochemistry of U and Th; the role of these elements for dating of minerals

2. Minerals most commonly used for chemical dating, containing radiogenic elements (monazite, xenotime, allanite, zircon, britholite, chevkinite), theory and application

3. Exercises with the use of an optical polarizing microscope – identification of accessory minerals that are commonly used in chemical dating

4. Practical use of a scanning electron microscope (SEM) – search and identification of accessory minerals that are commonly used in chemical dating; analysis of textures being the result of the diversity of the chemical composition. Analysis of element concentration maps of selected elements (Y, Th, U, Pb) that are of great importance for the determination of analytical points in chemical dating

5. Practical use of an electron microprobe for chemical dating – conditions of the analysis for individual mineral phases in order to establish the best detection limits for elements that are basic for age determination – Pb, Th, U

6. Run of microprobe analyses of selected minerals (monazite, xenotime, allanite, chevkinite)

7. Calculation of the age, assessment of the quality of the obtained results, critical data processing

8. Interpretation of the results, error estimation (with the use of Isoplot software)

9. Other analytical techniques (other than microprobe) used in chemical dating (ICP MS-LA).

On completing the course, the student:

- has knowledge in

- deciding whether chemical dating of a given rock is possible

- critical assessment of the obtained age results

- has skills in

- conducting the entire path of investigations to obtain the age of the analysed phases, through documentation, SEM investigations, EPMA analyses and age calculations

- operating the scanning electron microscope (in a basic range)

- co-operation with the operator of the electron microprobe

Obtaining a course credit requires participation in all tutorials, each time documented by the tutor in form of individual tutorial record sheets. The course is credited based on the preparation of a report that contains documentation of all stages of work to obtain the age of the investigated material. Each student is obliged to present a short summative talk (multimedia presentation) during a joint session of all tutees and their tutors, scheduled for the end of the academic year (June), in which the course takes place.

not applicable